The present invention relates to current carrying bus bars and more particularly to a bus bar capable of self-heating and self-soldering without undergoing thermal expansion.
Several problems exist with present methods available to heat bus bars for soldering to printed circuit boards and other electrical applications. A relatively large Copper bus is desired to carry large amounts of current, resulting in an extremely good electrical and thermal conductor. The heat sink effect which results from this large conductor prevents the bus pins from being uniformly heated.
Present conduction and wave solder techniques are unsatisfactory. Conduction soldering requires a high temperature iron due to the large thermal heat sink of the bus. The temperature gradient which forms across the pins causes improper solder joints especially at the cooler base of the pin. If the bus bar is heated by wave soldering uniform heating is attached across the pins and a good solder joint is formed, however, uniform heating is also attained across the entire length of the bus causing thermal expansion of the bus. When the bus cools and contracts, the board to which it is soldered warps undesirably.
Conventional direct heating which can minimize board warpage also requires that each pin be individually heated which is time consuming and prevents removal of the bus which can only be accomplished by desoldering all pins at once. Also direct conduction heating is applied to the tip of the bus pins and results in non-uniform pin heating and often the base of the pins will not achieve solder melt temperature due to the large thermal sink of the bar.